Inspection Procedure 3
Inspection Procedure 3: The Tight Corner Braking Phenomenon^Appears with the Drive Mode Selector in the FWD or AWD Position.
^ Tight corner braking phenomenon: When a AWD vehicle makes sharp cornering in a paved road at low speed (ex. parallel parking), there is a difference in turning radius between front and rear wheels. If such a difference can no longer be compensated by tire slippage, the vehicle behaves as if it is under braking.
^ The vehicle is tuned so that the tight corner braking phenomenon appears at a certain level with the drive mode selector in the LOCK position.
COMMENTS ON TROUBLE SYMPTOM
If the tight corner braking phenomenon occurs with the drive mode selector being on the FWD position, the electronic control coupling may have a problem. If the tight corner braking phenomenon occurs only with the drive mode selector being on the AWD position, the data received by AWD-ECU from each ECU, the electronic control coupling, or AWD-ECU may have a problem.
TROUBLESHOOTING HINTS
^ Malfunction of electronic control coupling
^ Malfunction of data transmitted from ABS system
^ Malfunction of data transmitted from the engine control system
^ AWD-ECU malfunction
DIAGNOSIS
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
STEP 1. Check for the tight corner braking phenomenon occurrence during driving on a flat road
Check if the tight corner braking phenomenon occurs during driving on a flat road with the drive mode selector being on the FWD or AWD position.
Q:Does the tight corner braking phenomenon occur?
YES: Go to Step 2.
NO: Go to Step 5.
STEP 2. Wiring harness check
NOTE: Prior to the wiring harness inspection, check the following connectors for improper engagement, terminal damage or terminal drawn in the connector case.
^ C-128 AWD-ECU connector
^ D-113 Joint connector
Check the wiring harness between the C-128 AWD-ECU connector (terminal No.1) and the D-119 electronic control coupling solenoid connector (terminal No.1) for damage or other problem.
Q:Is the wiring harness in good condition?
YES: Go to Step 3.
NO: Repair damage or other problem in the wiring harness. Then go to Step 7.
STEP 3. Scan tool MB991958 data list
Check the service data for the items below.
^ Item 16: FL wheel speed sensor
^ Item 17: FR wheel speed sensor
^ Item 18: RL wheel speed sensor
^ Item 19: RR wheel speed sensor
^ Item 26: Throttle position
Q:Does the service data meet the standard value range?
YES: Go to Step 5.
NO: Perform the troubleshooting of the ABS system or the troubleshooting of the engine control system. Then go to Step 4.
STEP 4. Check for the tight corner braking phenomenon occurrence during driving on a flat road
Check if the tight corner braking phenomenon occurs during driving on a flat road with the drive mode selector being on the FWD position.
Q:Does the tight corner braking phenomenon occur?
YES (Coil current is 0 A) : Measure the coil current when the tight corner braking occurs. If the coil current measures 0 A, replace the electronic control coupling. Then go to Step 5.
YES (Coil current is other than 0 A) : Measure the coil current when the tight corner braking occurs. If the coil current is other than 0 A, go to Step 5.
NO: Go to Step 6.
STEP 5. Retest the system.
Q:Does the malfunction occur again?
YES: Replace AWD-ECU. Then go to Step 6.
NO: The trouble can be an intermittent malfunction.
STEP 6. Retest the system.
Q:Does the malfunction occur again?
YES: Replace the electronic control coupling. Then go to Step 7.
NO: This diagnosis is complete.
STEP 7. Check whether the DTC is reset.
Q:Does the malfunction occur again?
YES: Diagnose again from Step 1.
NO: This diagnosis is complete.